My girlfriend had a one-night stand and it has destroyed my life

My girlfriend of two years recently had a one-night stand. I think she did it in revenge because her friends told her I had had an affair. She now knows that wasn’t true and deeply regrets what she did, and wants to put things right and see a therapist. She even installed a spy app on her phone that emails me a log of her calls. I have been 100% loyal to her and saw her as my future wife and the mother of my kids. She has destroyed my life. I don’t know if I should give her a second chance. I love her very much, but can’t get the images out of my mind.

I love her and saw her as my future wife, but I don’t know whether to give her a second chance